How best to auto create resized textures on import?

Unity Engine
1

I’m having some trouble determining how exactly do to this.

On import of a texture (identifiable by name) I want to auto create smaller versions of the texture, i.e. half size and quarter size. It they already exist (from a previous import) I want to modify them.

2 
    class InvertColor extends AssetPostprocessor {
        function OnPostprocessTexture (texture : Texture2D) {
            if(assetPath.Contains("specific_texture"))
                // change import settings here for the texture
        }
    }
3

Thanks.

How do I go about creating the 2 new smaller textures on import of the fullsize one?

4 
texture.Resize(texture.height/2,texture.width/2,TextureFormat.ARGB24,true);